Think antibody tests are key to opening the economy? Not so, health officials say

Antibody tests could be helpful in pinpointing the number of Washington residents who previously have had COVID-19, but they are not a “passport” for demonstrating that someone is immune, state and local government officials say.

The Food and Drug Administration earlier this week said companies that manufacture the tests will now have to demonstrate that they work before they are sold. The federal agency, which had allowed more than 100 commercial antibody tests to reach the market without review, said it took the step because some firms have marketed fraudulent test kits.

“That was good news to bring that a little bit under more control,” said Dr. Charissa Fotinos, a high-ranking state Health Care Authority official who is leading the statewide testing effort.

The tests — usually involving a finger-prick of blood on a test strip — search for proteins called antibodies that the body produces days or weeks after fighting an infection. They’re referred to as antibody, or serological, testing, and are separate from the nose swab tests used to confirm active cases of COVID-19.

Gov. Jay Inslee said Tuesday he spoke with Abbott Laboratories recently about the potential for large-scale “surveillance” antibody testing in Washington. Surveillance refers to the search for those people who have previously had COVID-19 — with or without becoming sick. The University of Washington’s Virology Division also is doing antibody testing.

“We think this can have potential utility as a surveillance tool to let us know what the presence of the disease really is,” said Inslee. “It’s also very important to guard against a second wave because sometimes you can have asymptomatic people for quite some time before you even recognize it’s present.”

A spokesman for Abbott Laboratories, an international pharmaceutical firm based in Illinois, didn’t return a message seeking comment.

Inslee said people need to realize that antibody testing, for now, cannot guarantee that a person has immunity from COVID-19.

“We have to realize it’s for surveillance purposes, not for a passport to go back to work,” he said.

It’s unclear how many Washington residents are getting antibody tests at this point, said Nigel Turner, communicable disease division director for the Tacoma-Pierce County Health Department.

Turner encouraged people to consult with their medical providers about any type of testing, adding that “some caution needs to be applied” in how people view antibody testing results.

“It’s important what this information isn’t going to tell us. Serology testing is really just measuring antibodies in the blood that develop over time. It’s not what we call a diagnostic test that really will tell somebody if they are currently infected,” he said.

Because scientists don’t yet know how long antibodies remain in the blood and the level of protection they provide, antibody testing can’t yet determine how much of the population is immune from COVID-19, Turner said in an interview and a blog post on the department’s website.

The Thurston County Health Department also advises residents that antibody tests have limitations.

“Because of the cross reactivity with ordinary coronavirus, it is difficult to tell if a positive test is due to COVID-19 or six other strains. ... Having a positive test does not mean that you are protected from getting COVID again,” the health department says on its website.

Cross-reactivity refers to the antibody test not distinguishing between the different strains of coronavirus.

Dr. Diana Yu, Thurston County’s Acting Health officer, said in an email that “antibody testing has its place in areas that are more heavily affected than we are in Thurston County. For our situation, it really does not give us added information. With false positives due to cross reaction, it might give people a false sense of security by making them think they are immune.”

This story was originally published May 7, 2020 at 5:45 AM with the headline "Think antibody tests are key to opening the economy? Not so, health officials say."